| Objectives: The drug of choice in the treatment of carcinoma of stomach, colon, rectum, breast, ovary, and urinary bladder is 5-fluorouracil. For several decades, 5-fluorouracil was the only chemotherapeutic agent with clinical activity against colorectal cancer. Numerous active 5-fluorouracil schedules are in clinical use, but erratic oral bioavailability has historically mandated intravenous administration. On intravenous administration 5-fluorouracil produce severe systemic toxic effects of gastrointestinal, hematological, neural, cardiac and dermatological origin. Most of these systemic side effects are due to the cytotoxic effect of 5-fluorouracil after it reaches unwanted sites. Targeted delivery of 5-fluorouracil not only reduces systemic side effects, but also provides an effective and safe therapy for colon cancer with reduced dose and reduced duration of therapy. Of the various routes of targeting drug, the oral route remains the choice of administration. In the recent years, oral colon-specific drug delivery System (OCDDS) has been investigated, because it can be used to the treatment of pathological changes of site in colon, for example carcinoma of colon and colonitis. It also is used broadly in oral drug delivery systemj of albumen and polypeptide drugs.Methods: Pellet core containing 5-fluorouracil and microcrystalline cellulose were prepared by the process of extrusion–spheronization. The mixture of a 2% w/v solution and Surelease? was used as a film coat. Coating was performed using fluidized bed coater. The orthogonal experiment was designed to screen technique in which the speed of extrusion, speed of spheronization and the time of spheronization were taken as three influential factors and three different levels were selected to part, each conformation of technique was selected refer to the L9 (34) orthogonal design table. By analysis of range, the optimization of technique was definite with the colligation evaluation of formation. The single factor experiment was designed to screen technique in the concentration of coating liquor, temperature of in air, pressure of spray and speed of transfuse. Film coated pellets of 5-fluorouracil containing various proportions (pectin-Sure- lease?, i.e. 1:0, 0:1, 1:1, 1:2, 1:3, 1:4 w/w) of pectin and ethylcellulose were prepared and subjected to in vitro drug release. Coated pellets (pectin to Surelease? 1:2 w/w) with the film thickness of TWG-5%, TWG-10%, TWG-20% and TWG-30% were prepared and subjected to in vitro drug release. The mobile phase consisted of a mixture of methanol and sodium acetate buffer (pH adjusted to 4.0) in the ratio of 30:70. The mobile phase was filtered and pumped at a flow rate of 0.8 mL·min-1. The column was maintained at a temperature of 25?C.The eluent was detected by UV detector at 266 nm. The retention time was found to be 4.21 min.Drug release studies in the presence of caecal content were also carried out using USP dissolution test apparatus. However, slight modification in the procedure was done. The experiments were carried out in 250 mL beaker immersed in water maintained in the jars of dissolution test apparatus. Initial studies were carried out in 150 mL of 0.1 mol·L-1 HCl (pH of 1.2) for 2 h. After this 50 mL of 0.2 mol·L-1 trisodium phosphates was added to the dissolution media and the pH adjusted to 6.8. The study at a pH of 6.8 was continued for 3 h after which caecal content equivalent in caecal content to 8 g was added to 200 mL of buffer (pH 6.8) to give a final caecal dilution of 4%. The experiments in caecal content media were carried out in presence of a continuous supply of CO2 for another 19 h. At different time intervals 1 mL sample was withdrawn from the dissolution medium and 1 mL of caecal content (4%), maintained under anaerobic conditions was replenished into the dissolution media. The volume of the sample was made up to 10 mL with buffer (pH 6.8), filtered through sintered glass (G-5) filter and the filtrate was analyzed using HPLC method described below: The chemical and physical stability of optimal formula was investigated under following circumstances: high humidity, high temperature, strong light and long natural store condition (40?C/75% RH for 6 months). At the end of the study period, the formulation was observed for change in physical appearance, color, drug content and drug release characteristics.The animals were administered orally coated and uncoated pellets via a polyethylene cannula (diameter: 2 mm) with 1mLwater under light ether anesthesia, respectively, at a dosage of 15 mg/kg. After oral administration of coated and uncoated pellets, three rats per time point were anesthetized by halothane, bled by heart puncture, and sacrificed. Heparinized blood samples were immediately centrifuged at 10,000 rpm for 10 min on a tabletop centrifuge, and the plasma was separated and transferred to microcentrifuge tubes. Major organs were collected including stomach, small intestine, cecum tissue, and colon tissue. Cecal contents and colon contents were also collected and all samples were weighed. All harvested samples were stored at -20?C and analyzed within one month. The 5-fluorouracil concentrations in all samples were determined by high performance liquid chromatography.The peak plasma 5-fluorouracil concentration (Cmax) and the time to reach peak levels (Tmax) were obtained from the plots of time versus plasma concentration of 5-fluorouracil. Pharmacokinetic parameters were calculated using 3p97 (Chinese Pharmacological Society). The software was used to analyze 5-fluorouracil plasma concentration vs. time data after oral administration of coated and uncoated pellets. The mean residence time and relative bioavailability were also determined.Results: The pellet core were prepared by extrusion/ spheronization: speed of extrusion 30 r/min; speed of spheronization 30 r/min, time of spheronization 5min; Aqueous coating formulations were heated to 40?C prior to the coating process which was operated with an inlet temperature of between 38 and 42?C, at a spraying rate of 1 mL/min and at atomizing air pressure of 0.5 kg.The pellet core were prepared by extrusion/ spheronization: speed of extrusion 30 r/min; speed of spheronization 30 r/min, time of spheronization 5 min; Aqueous coating formulations were heated to 40?C prior to the coating process which was operated with an inlet temperature of between 38 and 42?C, at a spraying rate of 1 mL/min and at atomizing air pressure of 0.5 kg.The results of the study show that the formulation of TWG-20% (pectin to Surelease? 1:2 w/w) is most likely to provide targeting of 5-fluorouracil for local action in the colon.The results of the system serve experiment of the HPLC method to determine the content of 5-fluorouracil: the reserve time of 5-fluorouracil were about 6min, the recoveries were 99.75~100.3%, the within-day precision was 1.25~2.14%, the between-day precision was 2.54~3.00%. The method could determine the content of 5-fluorouracil accurately and precisely.There was no change in the physical appearance of the formulation of TWG-20% at the end of the storage period. After storage period the formulation of TWG-20% was also subjected to assay of the drug content, in vitro drug release pattern. When the coated pellets of TWG-20% were stored at 40?C/75% RH for 6 months there was no change either in physical appearance or in drug content. When the dissolution study was conducted in simulated GI and colonic fluids as described above, no significant difference (p > 0.05) was observed in the cumulative percent of 5-fluorouracil released from the formulation of TWG-20% stored at 40?C/75% RH for 6 months when compared to that released from the same formulation before storage.The mean peak 5-fluorouracil concentrations in cecal contents, cecum tissue, colon contents, and colon tissue, respectively, were 5.33±2.5μg/g, 0.54±0.20μg/g, 4.66±2.10μg/g and 0.31±0.14μg/g for 5-fluorouracil released from the coated pellets, and 1.16±0.9μg/g, 0.34±0.09μg/g, 0.18±0.03μg/g and 0.10±0.05μg/g for the administration of the uncoated pellets. In plasma, the high and sharp drug concentration profile from uncoated pellets was in contrast to the relatively low and flat pharmacokinetic profile obtained from drug released from the coated pellets. In contrast, the observed mean Cmax from the coated pellets group (3.65±2.3μg/g) was lower than that of the uncoated pellets group (23.54±2.9μg/g). There was a statistically significant difference (p < 0.05) in the AUC values between the uncoated pellets (49.08±3.1μg/h/mL) and coated pellets (9.06±1.2μg/h/mL). The relative bioavailability of the coated pellets from the uncoated pellets is 18.1% by comparing the AUC under the assumption that the BA of 5-fluorouracil released from the uncoated pellets is 100%.Conclusions: Combination of ethylcellulose and pectin as a film coat may provide the necessary protection to a drug in the upper GI tract while allowing enzymatic breakdown and drug release in the colon. The distribution of coated pellets was markedly different from that of uncoated pellets after oral administration. In contrast to uncoated pellets dispersal along the whole upper GI tract, 5-fluorouracil was predominantly released from the coated pellets in cecum and colon. The absorption of drug from different regions of the GI tract was found to influence the pharmacokinetic profile and parameters. In conclusion, colon-specific delivery of 5-fluorouracil was achieved after oral administration of the coated pellets to the rats. The relatively high local drug concentration with prolonged exposure time provides a potential to enhance anti tumor efficacy with low systemic toxicity for the treatment of colon cancer, because longer exposures to lower concentrations favors DNA-directed effects which is thought to contribute to its anti tumor effect. |
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